The "VACU-FLUSH".RTM. toilet system for boats and recreational vehicles manufactured by Sealand Technology, Inc. of Big Prairie, Ohio, has for many years effectively provided a vacuum system facilitating flushing of a vacuum toilet and holding of the sewage from the toilet until there is a need or opportunity to properly dispose of it. Initially, this system included four main components, a vacuum toilet connected to a vacuum tank, in turn connected to a vacuum pump, in turn connected to a holding tank, such as shown in U.S. Pat. No. 4,819,279. The number of components was effectively reduced from four to three by efficiently combining the vacuum pump with the vacuum tank, such as shown in U.S. Pat. No. 5,408,704 and WO 96/41059 (the disclosures of which are both hereby incorporated by reference herein). The invention relates to a still further development of such a toilet system which is particularly suitable for use in boats and caravans or recreational vehicles, where space is at a premium or where relevant cost factors apply.
According to the present invention a single plastic combined vacuum tank and holding tank is provided. The tank is unreinforced--that means, as used in this specification and claims, that it has no reinforcing elongated fibers, such as glass or metal filaments, integrally incorporated with the plastic material (although other materials, such as talc or glass powder, may be utilized). The tank may also directly mount the vacuum pump. This means that the system has a minimum number of components (two), a vacuum toilet and a combined vacuum/holding tank and vacuum pump, or three if the vacuum pump is disposed distinct from the tank. While the number of components have been reduced according to the invention, the functionality of the system is not significantly compromised. Rather only cost saving, space saving, and operational advantages ensue.
While it has been known per se to use a combined vacuum and holding tank for sewage systems, the prior art constructions have included expensive tank materials and/or have necessarily been cylindrical (with domed ends), and do not have the low cost or space saving advantages according to the invention. For example U.S. Pat. No. 3,663,970 relates to a system in which a fiberglass or fiberglass reinforced combined vacuum and holding tank is provided, requiring the use of pressure to expel waste, and because of the materials utilized is expensive. U.S. Pat. No. 5,002,592 shows a cylindrical (with domed ends) metal tank connected to a blower and for also for holding sewage, while U.S. Pat. No. 5,214,807 shows a dual wall tank. While all plastic tanks per se have been known before for vehicle sewage systems, such as in U.S. Pat. No. 5,408,704, they were relatively small (only for vacuum in the U.S. Pat. No. 5,408,704), and it was unknown that an all unreinforced (e.g. rotational molded or injection molded) plastic larger tank was possible, such as a combined vacuum and holding tank as according to the invention.
It is possible to provide a non-cylindrical (e.g. generally parallelepiped) combined vacuum and holding tank of substantially unreinforced all plastic according to the invention by providing a tank having convoluted, discontinuous surfaces (e.g. the discontinuities provided by grooves, channels, or other discontinuities), so that the tank has no continuous flat surface area of more than about 80 square inches. The size (interior volume) of the tank according to the invention typically is about 45-65 liters (e.g. about 14 gallons), and normally, although not necessarily under all circumstances, the vacuum portion of the tank is about 12 liters or more (e.g. under the minimum vacuum portion situation the liquid/sewage portion of the tank is about 43 liters).
According to one aspect of the present invention a combined vacuum and holding tank assembly is provided comprising the following components: A substantially hollow unreinforced non-cylindrical all plastic tank having first and second (substantially planar) ends, first and second (substantially planar) sides, at least one pump-mounting surface, first and second outlets, an inlet, an upper surface, and a bottom. A vacuum pump mounted on the at least one pump-mounting surface exteriorly of the tank. A downwardly extending sewage transporting tube disposed within the tank connected to the first outlet. A gas inlet tube disposed within the tank and connected to the second outlet, and having a top open end adjacent (i.e. near) the tank upper surface. And a connection between the vacuum pump and the second outlet exterior of said tank.
If desired a sensor may be provided for sensing the level of liquid in the tank, as well as means for precluding operation of the vacuum pump if the sensed level within the tank becomes closer than a predetermined amount to the air inlet tube open top end so that a gas volume is always provided adjacent the upper surface inside the tank. If provided the means for precluding operation of the vacuum pump if the sensed level within the tank rises too high ensures that sewage doesn't pass out the vacuum pump (which is usually capable of pumping liquid too). For example in typical operation, the tank would have a waste holding capacity of about 40-45 liters (about 10 to 11 gallons), and operate with a minimum of about 12 liters (about three gallons) of vacuum, which is generated to between 20-26 cm (about 8-10 inches) of mercury (as is conventional per se). In response to the sensing of the level of the waste, a relay may be closed or opened to detach the vacuum pump from its power source so that it can no longer operate until the liquid level drops, or a controller may be provided to take information from the sensor and disable the vacuum pump in any known manner. The sensor too may be any conventional structure, such as an optical, sonar (including ultrasound), piezoelectric, fluidic, or mechanical sensor. For example a conventional float operated sensor can be utilized.
Typically a gas discharge tube is connected to the vacuum pump for discharging gas from the tank, e.g. penetrating an exterior partition wall of a boat (e.g. boat hull) or caravan or recreational vehicle (e.g. side panel or bottom) in which the tank is mounted, and a conduit is typically connected to the first outlet for discharging sewage from the tank. The at least one pump-mounting surface may comprise a top surface, and may include a second pump-mounting top surface. In that case an optional sewage discharge pump may be mounted on the second pump-mounting top surface and connected to the first outlet. A conduit is preferably provided connecting the inlet to at least one vacuum toilet.
The substantially unreinforced plastic tank may be rotational molded from linear low density polyethylene (with or without additives), although a wide variety of other plastics may be utilized, and other manufacturing techniques. Rotational molding is preferred, however, since it is easy and inexpensive and does not require seams in the tank (which must be sealed, as is necessary with injection molding). If the tank is injection molded (if sales volume justifies) a wide variety of plastics, including ABS, may be used. The convoluted, discontinuous construction of the tank surface typically includes reinforcing grooves or channels formed in the raised portion, and a similar grooved configuration is desirably provided for all surface of the tank. Also the first and second outlets are typically on opposite sides of a vertical plane substantially bisecting the tank and intersecting the first and second ends thereof, and face in opposite directions.
A vacuum switch is preferably mounted to the tank for sensing the level of vacuum in the gas volume. Any conventional construction of vacuum switch, or like device, may be utilized, the details of the vacuum sensing not being significant. Typically the vacuum switch is calibrated to start operation of the pump if the level of vacuum in the gas volume is lower than a predetermined amount (e.g. if lower than about twenty centimeters--eight inches--of mercury the vacuum pump is operated until the gas volume is evacuated to a level of about twenty five centimeters--roughly about ten inches--of mercury). The tank typically maintains a maximum level of vacuum of about twenty six cm of mercury.
Typically the bottom of the tank is formed with a slope toward a sump, and integral plastic legs support the tank on a horizontal surface so that the sump is the lowest part of the tank. The downwardly extending tube preferably comprises a dip tube having an end termination cut at an angle, defining a generally oval-shaped opening disposed just above the sump. In this manner the general configuration of the tank bottom and the dip tube configuration are such as illustrated in WO 96/41059.
According to another aspect of the present invention a sewage handling assembly is provided for a boat, RV or caravan, plane or train comprising the following components: At least one toilet having a waste discharge therefrom. An unreinforced non-cylindrical all plastic combined vacuum and holding tank including an inlet and first and second outlets. A conduit connecting the tank inlet to the toilet waste discharge. A vacuum pump connected to the second outlet. A gas handling conduit from the vacuum pump including an end termination penetrating the boat, plane, train or recreational vehicle exterior partition. A sewage handling conduit operatively connected to the first outlet and having an end termination penetrating the partition. And, the tank having a top and a bottom, sewage from the toilet provided in the bottom, and gas at less than atmospheric pressure provided in the top (usually, but not necessarily, at all times).
The details of the tank, etc., preferably are as described above, including having an interior volume of about 45-65 liters, a generally parallelepiped configuration, and a contoured, discontinuous, convoluted surface which has no continuous flat surface area of more than 80 square inches. Also a vacuum relief valve may be provided in the tank, and the tank may have rolling facilitating elements (such as wheels, casters or rollers).
It is the primary object of the present invention to provide the optimum in simplicity and cost effectiveness for the handling of sewage from one or more vacuum toilets, particularly in association with boats, recreational vehicles or caravans, planes, trains, and other vehicles. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.